Method of rolling



July 18, 1939. w, c. MCBAIN 2,166,418

METHOD OF ROLLING Filed April 21, 1934 INVENTOR MW at waw Patented July18, 1939 UNITED STATES PATENT OFFICE METHOD OF ROLLING Application April21, 1934, Serial No. 721,747

12 Claims.

My invention relates to a method of rolling strip metal and isespecially concerned with the cold rolling of strip in a reversing millequipped with either power-driven or idle work rolls, i. e., rollsdriven by the forward tension applied to the strip.

It is now well known that it is advantageous to subject strip to tensionwhile rolling. My method is an improvement over the present practice andhas the added advantage of making it possible to subject only very smallportions of the strip entering and leaving the rolls to a tensile stressexceeding the elastic limit, whereas the strip as a whole is subjectedto a tension not exceeding the elastice limit during the actual rolling.Another advantage of this method of tensioning is that it producesflatter strip. The reason is that there is a permanent deformation of aportion of the metal in the strip, at a point opposite the first pointof contact of the strip with the work roll. There is another slightpermanent deformation of a portion of the metal in the strip at thepoint where the metal in the strip straightens out and departs fromcontact with the work roll. Since this bending action progressesuniformly over the entire length of strip, I exert the same effect onall portions thereof. At the same time, the strip is not subject to thehazard of breaking which would inevitably accompany the stretchingthereof throughout its entire cross-sectional area, beyond its elasticlimit.

My invention also provides a very simple and effective method of guidingthe strip into the rolls. I preferably use top and bottom guides on thefirst or loading pass after which the guides may be removed and thestrip held by tension against one of the rolls for accurate guiding intothe pass or place where both surfaces of the strip are in contact withwork rolls. The principal advantages of this kind of guiding are first,the high degree of uniformity of the precisely ground roll surface incontact with the strip before it enters its pass, and second, the factthat the strip by this method is guided clear into the pass area,whereas, with the usual guides, it is impossible to guide the strip allthe way into the pass area. Another valuable feature of my method ofrolling strip is the compactness and simplicity of the equipmentrequired to do the rolling and tensioning. The tension is preferablyreduced with each succeeding pass to suit the thinner section. Also thetension is varied as necessary to regulate the roll pressure and,consequently, the spring of the rolls and the shape of the pass and,therefore, the shape of the finished strip.

In the drawing- Figure 1 is a diagram of the apparatus which I prefer touse in performing my method of rolllng strip, particularly in the firstor loading pass;

Figure 2 is a similar view showing the operations on the second pass andsubsequent passes; and

Figure 3 is an enlarged diagrammatic view of the strip passing throughthe rolls on the second pass and is typical of the subsequent passes.

Referring again to Figure -1 which shows the first or loading pass, thecoil of strip to be rolled is first placed on an uncoiler I. In the formshown, the uncoiler consists of a coil box 2 and a roller leveler 4. Thecoil box consists of a housing carrying a multiplicity of rollers 3,either power-driven or idling, said rollers being suit ably located toreceive a coil 5. These rollers have rolling contact with the coil ofstrip as it is fed into the roller leveler 4 and a mill 1. The rollerleveler consists of a series of staggered rollers 6 that have rollingcontact with the strip 5 and straighten the strip for the passagethrough guides 8 into the mill 1. The mill I is representeddiagrammatically by the two work rolls 9 and I0 and the two backing-uprolls H and I2. It also has winding and unwinding reels I3 and M. Thereels l3 and M are equipped with grippers l5 and I6. The guides 8 areremovable.

In the loading pass, as show in Figure 1, the right-hand reel l4 only isin use for coiling up the strip after it leaves the mill. The left-handreel I3 is not used until the second pass. Figure 2 represents thesecond pass, the mill I having been reversed and one strip end now beingattached to each of the two reels l3 and M by grippers l5 and Hi. Inthis pass the motion of the strip is from right to left as shown by thearrow. This pass is typical of the subsequent passes back and forthuntil the rolling is completed and the finished coil is removed from themill. In some cases, I drive the winding reel and retard the unwindingreel, as shown in my U. S. Patent No. 1,881,056, to tension the strip asit is being rolled.

Figure 3 is an enlarged diagrammatic view of the second pass of thestrip through the mill. This view shows the top and bottom work rolls 9and I0 and the strip 5. The upper work roll 9 is in contact with thestrip 5 through the arc of contact X and the lower roll is in contactwith the strip through the arc of contact Y. The strip 5 is deflected asit comes in contact with the roll II) at the point of contact A.Sufficient tension is applied to the strip 5 so that there is an actualstretching of the surface of the strip at point M opposite point ofcontact A. The strip is thus given a permanent set or deformation andtherefore conforms to the curvature of the roll I0. As the strip leavesthe arc of contact Y with the work roll I0 a similar stretching takesplace at the point B removing the curved set previously imparted, againdeforming the strip into flat condition. This result might also beobtained by 'the mill on opposite sides thereof. ,does not exceed theelastic limit throughout the permitting the outgoing strip to curvepartially around the upper roll 9. The tension in the strip ispreferably kept low enough so that this stretching eifect'does notextend clear through the thickness of the strip. If it did, the bendingaction of the strip, as it comes in contact with and leaves the roll,would no longer be of aid in causing the proper distribution of thestretching. In other words, if the tension were great enough to causethe areas of permanent elongation M and B to extend clear across thestrip, then immediately the entire straight portion of the strip wouldbe subject to the same excessive tension and liability of rupture wouldbecome so great that the method would become of doubtful value. As shownin the drawing, the axes of the reels, backing-up rolls and work rollsare parallel. Tracking of the strip through the pass is assisted by theproper operation of the screwdown. This, in combination with the use ofthe high tension in the strip, as previously mentioned, reducesmaterially the amount of work required to be done by the side guides andin some cases makes it possible to eliminate them altogether.

It will be apparent from the foregoing description that the inventiondescribed herein is characterized by important advantages over thepreviously practiced methods of rolling strip, According to my method,the strip is subjected progressively to a tensile stress exceeding theelastic' limit but confined to points in the strip adjacent The tensionthickness of the strip at any one point or at any one instant, and,therefore, lower total tensions can be employed than heretofore toaccomplish the desired results. This results in a simplification of theproblem of strip breakage. This problem is very vexing when it isattempted to roll strip under tension in the neighborhood of the elasticlimit throughout the entire crosssectional area of the strip.

Although I have illustrated and described herein but one preferredpractice of my invention, it will be apparent that changes in thedescribed practice may be made without departing from the spirit of theinvention or the scope of the appended claims.

I claim: l

1. In a method of rolling strip, the steps including entering stripwhile cold between reducing rolls and pulling it therefrom at an angleto the common tangent to said rolls, and subjecting the strip duringrolling to a tension such that the tensile stress in the strip exceedsthe elastic limit of the material only adjacent the points at which thestrip is bent around one of said rolls.

2. In a method of rolling strip, the steps including pulling the'stripwhile cold between reducing rolls, subjecting the material to aretarding tension, and bending the strip about at least one of saidrolls to increase the stress in the strip at the points of bendingbeyond the elastic limit of the strip.

3. In a method of making strip, the steps including subjecting a lengthof strip while cold to combined tensile and compressive forcesinsufficient together to elongate the strip, and simultaneously bendingthe strip sufficiently to effect elongation in combination with saidtensile and compressive forces.

4. In a method of rolling strip, the steps including passing the stripwhile cold between reducing rolls, bending the strip between the rollspartially about one of them, and subjecting the strip to tension androll pressure sufficient to cause elongation only when combined with theeifect of the bending of the strip.

5. In a method of making thin sheet metal, the steps including passing astrip while cold between reducing rolls, applying forward tension to thestrip emerging from the rolls, simultaneously bending the strip aroundone of said rolls, and so regulating the roll pressure and tension thatthe tension in the strip exceeds the elastic limit only adjacent thepoints of bending, whereby to reduce the tendency to strip breakageduring rolling.

6. In a method of making strip, the steps including passing the stripbetween reducing rolls, exerting a compressive force on the strip whilepassing between said rolls, subjecting the strip to a tensile force,bending the strip around one of said rolls, and so regulating saidtensile and compressive force that the tensile force is sufficient toelongate the strip only when combined with the effect of said bending.

7. A method of rolling metal strip, including the steps of passing itbetween rolls, applying "tension to the metal and bending it partlyaround one of said rolls, applying sufficient pressure to the rolls toreduce the metal and thereby elongate Said strip only when combined withthe bending and tension in the strip at the points of tangency where thestrip comes in contact with and leaves said rolls.

8. In a method of cold rolling strip, the steps including subjecting alength of strip to combined tensile and compressive forces andsimultaneously bending the strip, said tension and said bending beingsuflicient by themselves to cause a measurable elongation apart fromthat produced by the compressive force.

9. In. a method of rolling strip, the steps including passing the stripwhile cold between reducing rolls, bending the strip partially about oneof them and subjecting the strip to tension sufficient, in combinationwith said bending, to cause elongation in addition to that produced bythe roll pressure.

10. A method of cold working strip metal, including passing the stripbetween reducing rolls under tension, bending said strip around anappreciable arc of one roll both before and after it contacts the secondroll and producing permanent elongations in said strip at points wherethe strip meets said first roll and where it leaves said first roll, inaddition to the elongation produced in the strip in the area where it isin contact with both rolls.

11. In a method of cold rolling strip, the steps including passing thestrip between reducing rolls, exerting a compressive force on the stripwhile passing between said rolls, subjecting the strip to a tensileforce, bending the strip around one of said rolls, and so regulatingsaid tensile force that the tensile force and the bending of the striparound the roll combine to produce an elongation in said strip inaddition to that produced in the pressure area where the strip is incontact with both rolls,

12. In a method of rolling strip while cold, the steps including pullingthe strip between reducing rolls, subjecting it to a retarding tension,bending it about at least one of the said rolls to increase the stressin the strip at the points of bending, beyond the elastic limit of thestrip, and controlling the roll pressure to assist in holding the stripcentrally of the mill.

WILLIAM C. MCBAIN.

